摘要:

AbstractThe distribution of Spinocerebellar projections from birth to adulthood in rats was analyzed by anterograde and retrograde tracing methods. A correlation between mossy fiber synaptogenesis and the establishment of Spinocerebellar topography was also investigated with electron microscopy.Experiments with retrograde transport techniques indicate that the spinal axons reach the cerebellum in two successive groups: the first one, appearing prenatally, contains axons from neurons in the central cervical nucleus, Clarke's column, the sacral nucleus of Stilling, as well as from border cells. The second group, which reaches the cerebellum by P3, arises from new neurons of the same nuclear regions and from scattered cells of the spinal gray matter. The distribution and the morphological appearance of the spinal cells change between P1 and P3 and give the adult pattern by P7.The establishment of Spinocerebellar projections occurs in four successive stages. In a first stage, spinal axons reach the cerebellum and occupy the prospective white matter of the anterior vermal lobe and of the pyramis. Later, during a “waiting” stage between P1 and P3, the spinal fibers become denser in the central white matter of both their anterior and posterior target zones but do not penetrate the gray matter. From P3 to P5 the protocolumnar stage takes place, and spinal axons invade the granular layer of the anterior lobe, where they begin to be organized in nascent sagittal columns. At the end of this stage, identifiable synaptic contacts between mossy terminals and granule cell dendrites are first observed in the anterior lobe by electon microscopy. In the pyramis, invasion of the granular layer begins only at P5. Between P5 and P7 the low intercolumnar dispersion of spinal fibers disappears and the projection roaches its fourth and final stage, characterized by a columnar organization corresponding to the adult pattern of the spinocerebellar projection.These results indicate that (1) the adult pattern of spinocerebellar projections is attained by P7. (2) The asynchronous invasion of the gray matter in the anterior and posterior lobes may be related to the chronology of mossy fiber maturation in these regions. (3) There is a temporal correlation between the columnar organization of the spinal axons and the appearance of the earliest‐maturing mossy rosettes. However, a clear relationship between synaptogenesis and topographic organization could not be demonst

ISSN:0092-7317    

DOI:10.1002/cne.902370302

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractAscending projections of the cochlear nuclei in the mustache bat were analyzed by anterograde transport of [3H]‐leucine and by retrograde transport of HRP. We were particularly interested in pathways to two parts of the system: (1) to the medial superior olive, because this nucleus is missing in most echolocating bats, but appears to be present in the mustache bat, and (2) to the intermediate and ventral nuclei of the lateral lemniscus, because these nuclei are hypertrophied and highly differentiated in all echolocating bats that we have examined. The results show a highly systematic projection from the anteroventral cochlear nucleus to all of the auditory nuclei in the brain stem. After an injection of [3H]‐leucine in the anterior and dorsal part of the anteroventral cochlear nucleus, presumably in a region sensitive to low frequencies, label is seen in the following locations: ipsilateral to the injection in the lateral part of the lateral superior olive; bilaterally in the dorsal part of the medial superior olive; contralateral to the injection in the dorsal parts of the intermediate and ventral nuclei of the lateral lemniscus; and in the anterolateral part of the central nucleus of the inferior colliculus. After an injection of [3H]‐leucine in a posterior part of the anteroventral cochlear nucleus, presumably in a region sensitive to high frequencies, labeling is in the same set of nuclei, but within each nucleus the label is now in a different location; medially in the lateral superior olive, ventrally in the medial superior olive, ventrally in each division of the ventral and intermediate nuclei of the lateral lemniscus, and medially in the central nucleus of the inferior colliculus. Projections from the entire anteroventral cochlear nucleus to the inferior colliculus are confined to the ventral two‐thirds of the central nucleus. The dorsal one‐third of the central nucleus of the inferior colliculus is the principal target of the dorsal cochlear nucleus and may be a target of the posteroventral cochlear nucleus. Both of these nuclei appear to project sparsely to the ventral parts of the inferior colliculus.We conclude first that the bilateral input to the medial superior olive in the mustache bat is similar to the input seen in other mammals. Thus this bat has a neural structure which is associated with the analysis of binaural time differences and which usually is seen only in animals with heads large enough to create interaural time differences greater than those available toPteronotus. Second, the projections from the anteroventral cochlear nucleus diverge to three separate targets in the lateral lemniscus: one in the intermediate nucleus and two in the ventral nucleus of the lateral lemniscus. These three target areas of the lateral lemniscus then project as three parallel pathways to the inferior c

ISSN:0092-7317    

DOI:10.1002/cne.902370303

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractExtracellular single‐unit recordings were made from 121 neurones in the thoracic spiral cord of the cat. All neurones could be driven by electrical stimulation of dorsal root afferent fibres. The neurones were classified, according to the absence or presence of inputs from the ipsilateral splanchnic nerve, as “somatic” or “viscerosomatic,” respectively.Cutaneous receptive fields were identified for 75 of the neurones: 31 were somatic and 44 viscerosomatic. Only two of the somatic cells received cutaneous nociceptive inputs, compared with 33 of the viscerosomatic cells. Sixty‐four percent of the whole sample of neurones had receptive fields which included three or more dermatomes. Viscerosomatic cells tended to have larger receptive fields than the somatic neurones, and six of them had fields which did not include the corresponding (T11) dermatome.Neurones with receptive fields in the dorsal one‐third of the dermatome tended to be located in the lateral one‐third of the dorsal horn, but those with receptive fields in the ventral two‐thirds of the dermatome showed no differential distribution within the gray matter. This is discussed with respect to the results of anatomical studies on the dorsal horn projections of cutaneous afferent fibres from different regions of the dermatome.Preliminary results from intracellular staining with horseradish peroxidase reveal extensive branching of primary afferents in the dorsal horn, and large dendritic fields of dorsal horn neurones. Our physiological and morphological results indicate that the somatotopic organisation of the thoracic spinal cord is less well defined than that of the l

ISSN:0092-7317    

DOI:10.1002/cne.902370304

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractForty‐six human temporal bones from 24 individuals were removed at autopsy and prepared for electron microscopy. The adequacy of histologic preservation was evaluated by light and electron microscopy. Characteristic autolytic changes included vacuolization of afferent neurons and neural poles of inner and outer hair cells, lysis of limiting membranes of hair and supporting cells, swelling of endoplasmic reticulum, and dissolution of mitochondrial cristae.The rate of autolysis varied significantly within cellular components of the inner ear. The neural poles of hair cells demonstrated more rapid autolysis than apical poles and nerve terminals showed more autolysis than myelinated nerve fibers. Postmortem time and the cause of death affected the adequacy of histologic preservation. Fixation in patients dying of pneumonia, hypoxia, head injury, or malignancy tended to be poor, whereas the fixation achieved in patients dying of cardiac disease with postmortem time of under 140 minutes was generally goo

ISSN:0092-7317    

DOI:10.1002/cne.902370305

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractQuantitative analyses of electron microscopic (EM) autoradiographs were used to identify the afferents from the dorsal cochlear nucleus in the central nucleus of the inferior colliculus (IC) in the cat. In order to localize the sources of radioactivity, material from axonal transport experiments was analyzed by means of a hypothetical grain procedure which takes the cross‐scatter of beta particles into account. Measurements of the synaptic vesicles in axonal endings and a cluster analysis were used to identify different groups of endings. In order to determine which types of endings arise in the dorsal cochlear nucleus, axonal endings labeled after axonal transport and unlabeled endings were characterized and compared to the groups defined by the cluster analysis.Axonal endings with round synaptic vesicles were labeled with more than 2 grains/μm2which was about 30% of the radioactivity in the central nucleus of the IC. This was six to seven times greater than if the radioactivity had been randomly distributed. Other tissue compartments usually had less radioactivity. Some myelinated and unmyelinated axons were labeled, but, as a group they had lower amounts of radioactivity than predicted by random labeling. In most cases, only low levels of activity were found in glial and postsynaptic structures.Five groups of axonal endings in the medial part of the central nucleus were identified by an analysis which clustered similar types of endings. The variance of the longest axis, the mean diameter, the variance of area, and the mean area of the synaptic vesicles were the variables most useful in distinguishing these five groups, Axonal endings with round synaptic vesicles were classified as either small, or large, or very large, while endings with pleomorphic vesicles were either large or small. Using measurements of the cross‐sectional diameter of dendritic microtubules, samples of digitized axonal endings from normal and experimental cases were normalized and could be compared directly to the groups defined by the cluster analysis. Microtubules were 21.7 nm (±1.6) in average diameter. After injections of3H‐leucine and/or proline in the dorsal cochlear nucleus, most of the labeled endings in the IC contained small, round vesicles (less than 47 nm in diameter) although a very small number of endings with large, round vesicles also were labeled. The numerous fusiform cells of the dorsal cochlear nucleus which project to the IC are the likely source of the labeled endings with small, round synaptic vesicles. Small numbers of labeled endings with large, round synaptic vesicles may originate from giant cells in the dorsal cochlear nucleus. Unlabeled endings may arise from other brain stem neurons or from intrinsic cells.The quantitative analysis of axonal endings provides a standard set of criteria for their identification in different experiments. In combination with experimental labeling methods, it may permit synaptic vesicle morphology to be associated with a specific neuron type. This information is a prerequi‐ site for defining the neural basis of information processing

ISSN:0092-7317    

DOI:10.1002/cne.902370306

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe morphology of the neurons in the perihypoglossal nuclei (nucleus prepositus, nucleus intercalatus, and nucleus of Roller) of the cat was studied in normal Nissl material, and by intracellular injection of horseradish peroxidase.The neurons in the nucleus prepositus were morphologically heterogeneous. Many of the cells in the ventromedial part of the caudal prepositus had relatively large somata, and complex dendritic trees which arose from numerous proximal dendrites and ramified extensively in the ventromedial aspect of the prepositus. These neurons had thick axons which typically did not give rise to local collaterals. The cells in the dorsolateral part of the caudal prepositus tended to have small somata, and dendritic trees which arborized in that region of the nucleus. The axons of these small cells frequently gave rise to local collaterals which terminated in the prepositus. Most of the cells in the prepositus had medium‐sized somata and relatively few dendrites which branched in an isodendritic manner and extended for long distances, frequently leaving the nucleus. These “principal” prepositus neurons had axons which arborized unilaterally, and often gave rise to collaterals which terminated in either the ipsilateral or contralateral prepositus. The neurons in the nucleus of Roller and nucleus intercalatus which were intracellularly injected with horseradish peroxidase resembled the multidendritic and small prepositus cells, respectively.The intrinsic connectivity of the perihypoglossal nuclei was also studied by injecting horseradish peroxidase or3H‐leucine into the prepositus nucleus. The results of these experiments suggest that the perihypoglossal nuclei are highly interconnected bilaterally, although the large cells in the ventromedial prepositus and the nucleus of Roller contribute little to these intrinsic connections, and are not major recipients of intrinsic inputs. On the other hand, the magnitude of the reciprocal connections between the prepositus and the nucleus intercalatus suggests that they are functionally

ISSN:0092-7317    

DOI:10.1002/cne.902370307

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe afferent and efferent connections of the nucleus prepositus hypoglossi with brainstem nuclei were studied using anterograde and retrograde axonal transport techniques, and by intracellular recordings and injections of horseradish peroxidase into prepositus hypoglossi neurons.The results of experiments in which horseradish peroxidase was injected into the prepositus hypoglossi suggest that the major inputs to the prepositus hypoglossi arise from the ipsi‐ and contralateral perihypoglossal nuclei (particularly the prepositus hypoglossi and intercalatus), vestibular nuclei (particularly the medial, inferior, and ventrolateral nuclei), the paramedian medullary and pontine reticular formation, and from the cerebellar cortex (flocculus, paraflocculus, and crus I; the nodulus was not available for study). Regions containing fewer labeled cells included the interstitial n. of Cajal, the rostral interstitial n. of the medial longitudinal fasciculus, the n. of the posterior commissure, the superior colliculus, the n. of the optic tract, the extraocular motor nuclei, the spinal trigeminal n., and the central cervical n.The efferent connections of the prepositus hypoglossi were studied by injecting3H‐leucine into the prepositus hypoglossi, and by following the axons of intracellularly injected prepositus hypoglossi neurons. The results suggest that in addition to the cerebellar cortex, the most important extrinsic targets of prepositus hypoglossi efferents are the vestibular nuclei (particularly the medial, inferior, and ventrolateral nuclei, and the area X), the inferior olive (contralateral dorsal cap of Kooy and ipsilateral subnucleus b of the medial accessory olive), the paramedian medullary and pontine reticular formation, the reticular formation surrounding the parabigeminal n., the contralateral superior colliculus and pretectum, the extraocular motor nuclei (particularly the contralateral abducens nucleus and the ipsilateral medial rectus subdivision of the oculomotor nucleus), the ventral lateral geniculate n., and the central lateral thalamic nucleus. Other areas which were lightly labeled in the autoradiographic experiments were the contralateral spinal trigeminal n., the n. raphe pontis, the Edinger Westphal n., the zona incerta, and the paracentral thalamic n. Many of the efferent connections of the prepositus hypoglossi appear to arise from principal prepositus hypoglossi neurons whose axons collateralize extensively in the brainstem. On the other hand, small prepositus hypoglossi neurons project to the inferior olive, and multidendritic neurons project to the cerebellar flocculus, apparently without collateralizing in the brainstem.The functional significance of the connections is discussed in light of the physiological activity of prepositus hypoglossi neurons and the physiological activity of the areas the prepositus hypoglossi receives inputs from and projects to. We conclude that the afferents to the prepositus hypoglossi arise primarily from regions of the brain which are involved in the immediate supranuclear control of eye and head movements, and that most of the targets of prepositus hypoglossi projections contain neurons whose activity is related to eye movements. We suggest that the function of the prepositus hypoglossi may be to construct an efference copy of oculomotor activity, and to distribute this signal to areas of the brainstem which are involved in various aspects of gaze cont

ISSN:0092-7317    

DOI:10.1002/cne.902370308

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractCorticothalamic connections of posterior parietal regions were studied in the rhesus monkey by using the autoradiographic technique. Our observations indicate that the rostral superior parietal lobule (SPL) is connected with the ventroposterolateral (VPL) thalamic nucleus. In addition, whereas the rostral SPL is connected with the ventrolateral (VL) and lateral posterior (LP) thalamic nuclei, the rostral IPL has connections with the ventroposteroinferior (VPI), ventroposteromedial parvicellular (VPMpc), and suprageniculate (SG) nuclei as well as the VL nucleus. The caudal SPL and the midportion of IPL show projections mainly to the lateral posterior (LP) and oral pulvinar (PO) nuclei, respectively. These areas also have minor projections to the medial pulvinar (PM) nucleus. Finally, the medial SPL and the caudal IPL project heavily to the PM nucleus, dorsally and ventrally, respectively. In addition, the medial SPL has some connections with the LP nucleus, whereas the caudal IPL has projections to the lateral dorsal (LD) nucleus. Furthermore, the caudal and medial SPL and the caudal IPL regions have additional projections to the reticular and intralaminar nuclei–the caudal SPL predominantly to the reticular, and the caudal IPL mainly to the intralaminar nuclei.These results indicate that the rostral‐to‐caudal flow of cortical connectivity within the superior and inferior parietal lobules is paralleled by a rostral‐to‐caudal progression of thalamic connectivity. That is, rostral parietal association cortices project primarily to modality‐specific thalamic nuclei, whereas more caudal regions project most strongly to associative thal

ISSN:0092-7317    

DOI:10.1002/cne.902370309

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902370301

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY